Remove last `if let strongSelf = self` usages

[mokagio]

Fixes #19549 — I'm working through the iOS Core project, to consolidate into a project in the Automattic org. This task was simpler to address than to migrate. Not really a 2-minute task, but close enough.

To test: Green CI will suffice. Also notice there should be no SwiftLint warnings.

I intentionally opened the PR with the new rule but no fix to verify the linter. Before applying the fixes:

Now, the linter is green. See the checks below.

P.S. Sorry for the huuuge diff. I started this out with strongSelf in mind. But since opening the task, SwiftLint upgraded the rule to include all optional binding. There were two strongSelf instances left which made me think it be a small little PR. But there were hundreds more if let x = x around the codebase. 😓

Regression Notes

1. Potential unintended areas of impact N.A.

2. What I did to test those areas of impact (or what existing automated tests I relied on) N.A.

3. What automated tests I added (or what prevented me from doing so) N.A.

PR submission checklist:

N.A.

• [x] I have completed the Regression Notes.
• [x] I have considered adding unit tests for my changes.
• [x] I have considered adding accessibility improvements for my changes.
• [x] I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

Testing checklist:

• N.A.

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress Alpha by scanning the QR code below to install the corresponding build.

	App Name	WordPress Alpha
	Configuration	Release-Alpha
	Build Number	pr23836-ca3718e
	Version	25.4.2
	Bundle ID	org.wordpress.alpha
	Commit	ca3718ef441aea6c0afcc172a50754c3cc0e3ed5
	App Center Build	WPiOS - One-Offs #11091

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[dangermattic]

	2 Warnings
:warning:	View files have been modified, but no screenshot or video is included in the pull request. Consider adding some for clarity.
:warning:	This PR is larger than 500 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.

Generated by :no_entry_sign: Danger

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack Alpha by scanning the QR code below to install the corresponding build.

	App Name	Jetpack Alpha
	Configuration	Release-Alpha
	Build Number	pr23836-ca3718e
	Version	25.4.2
	Bundle ID	com.jetpack.alpha
	Commit	ca3718ef441aea6c0afcc172a50754c3cc0e3ed5
	App Center Build	jetpack-installable-builds #10131

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